Driving and the elderly

Apoptotic cell changes occurring under certain developmental, physiological, and pathological conditions have been of increasing interest during recent years. Due to occasional difficulties in detecting apoptosis in routinely stained sections, various methods have been developed to facilitate tissue examination. Fragmentation of DNA during the process of apoptosis is a prerequisite for detection in the in situ end-labeling (ISEL) procedure. It is yet unclear whether other mechanisms of cell change that induce DNA fragmentation such as necrosis and postmortem autolysis also show positive staining with the ISEL technique. To investigate whether the ISEL assay visualizes autolytic DNA changes along with apoptotic DNA fragmentation, we tested the technique on brain tissue of mice after different time intervals (0, 6, 12, 24, 48, 72 h) of postmortem delay (PMD) and at 2 different temperatures of postmortem storage (4 degrees C and room temperature (RT)). Our semiquantitative results show that up to 24 h of PMD no prominent difference in labeling is observable at both temperatures. After 48 and 72 h of PMD at RT clusters of labeled cells begin to appear. Clusters of stained cells should therefore not be considered as apoptosis when using the ISEL assay.     

A regional study of developing rat brain: the accumulation and distribution of proteolipid proteins

The accumulation and distribution of proteolipid proteins in rat brain and selected brain regions (cerebellum, cerebral cortex, basal ganglia, and hippocampus) were studied during early postnatal development. In whole brain an eightfold increase of proteolipid was observed between ten and 33 days after birth. This was reflected in the separate regions examined where the proteolipid protein content increased six- to ten-fold during the same period. The basal ganglia and cerebral cortex contributed the greatest amount to the total proteolipid present. However, at 28-33 days the greatest concentration (mg/g tissue) was observed in the basal ganglia and hippocampus. When the proteolipid protein preparations were examined by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis, distinctive, heterogeneous patterns for each brain region were obtained. Proteolipid from basal ganglia (the region richest in white matter) consisted primarily of two major protein bands with apparent molecular weights of approximately 21,500 and 26,000. Both of these bands dramatically increased in quantity during myelination, and the larger protein coelectrophoresed with isolated myelin proteolipid protein. Both bands were also found present in proteolipid preparations from the other brain regions but in varying amounts relative to the total. The data suggest that the increase in proteolipid observed during this developmental period was due in large measure to the accumulation of myelin-specific proteolipids, but also that a significant proportion of the increase was due to the accumulation of nonmyelin components.     

The influence of post-mortem conditions on contractile and relaxant responsiveness of guinea-pig isolated tracheal smooth muscle

Responsiveness to various contractile and relaxant agonists was assessed in tracheal preparations from guinea-pigs that had been incubated in situ at 4-37 degrees C for 0-168 h post-mortem. The potencies of histamine and acetylcholine were increased up to 168 h at 4 degrees C post-mortem and up to 24 h post-mortem at 22 degrees C. Histamine potency also increased with increasing post-mortem time at 37 degrees C. After 48 h at 22 degrees C and 8 h at 37 degrees C, responses to all spasmogens were abolished. Increases in histamine and acetylcholine potencies were similarly observed in tracheal tissue that had been removed at death and then incubated at 4 degrees C in oxygenated Krebs-bicarbonate solution for 0-168 h. The increased potency of these drugs may be explained by epithelial damage and/or loss of an epithelium-derived inhibitory factor (EpDIF). Both basal and spasmogen-stimulated increases in intracellular phosphoinositides fell with increasing time and ambient temperature post-mortem, despite the fact that contraction in response to these agonists could still be evoked. This suggests the selective failure of this signal transduction pathway and the maintenance of responsiveness via other mechanisms. The potencies and maximum effects of relaxant agonists remained unaltered in tracheal tissue with increasing time post-mortem, suggesting little change in the function of the appropriate receptor-signal transduction processes. This study has therefore demonstrated that at 4 degrees C. contractile and relaxant responses were preserved for up to 168 h post-mortem, although the modulatory influence of the epithelium on histamine and acetylcholine responses was rapidly lost.     

Biodistribution of radiolabeled lipid-DNA complexes and DNA in mice

The tissue biodistribution and expression of [33P]DNA-1-[2-[9-(Z)-octadecenoyloxy]ethyl]]-2-[8](Z)-heptadece nyl]-3 -[hydroxyethyl]imidazolinium chloride (DOTIM):cholesterol complexes and 33P-radiolabeled DNA expressing chloramphenicol acetyl transferase (CAT; 4.7 kB) were studied after intravenous (iv) injection in ICR mice. Mice were injected with 200 microL of complex containing DNA at 3 mg/kg or DNA alone. One group received 8 microCi of radioactivity and were sacrificed at 5 and 20 min, and 1, 2, 4 and 24 h post-dose (n = 4/time point). A second group received the equivalent of 3.9 microCi of radioactivity and were sacrificed at 20 min, and 2 and 24 h for subsequent whole body autoradiographic analysis (WBA; n = 2/time point). The tissue distribution of intact DNA was assessed by Southern blot at 24 h post-dose, whereas the integrity of complexes and DNA incubated in heparinized whole blood was studied separately. In further studies, the time course of expression in lung tissue over a 48-h period was examined, and the relative lung-expression of purified open circular (OC) versus supercoiled (SC) DNA at 24 h was evaluated. Approximately 42% of the radioactivity was found in the lungs 5 min after injection and about half this percentage was found in the liver. By 2 h, only 5% remained in the lungs, but 48% was present in the liver. No other tissue accumulated >5% of the dose throughout the duration of the study. WBA radiograms confirmed the tissue distribution results and highlighted significant accumulation of radioactivity in bone over time. Southern Blot analysis demonstrated intact DNA in many tissues 24 h after dosing. In contrast, the majority of DNA incubated in blood was degraded within 2 h, although the complexes afforded some protection relative to DNA alone. The OC DNA expressed equivalently to SC DNA in lung tissue (OC = 1035 +/- 183 pg; SC = 856 +/- 257 pg/mg soluble protein, n = 6, mean +/- SEM) at 24 h, and detectable levels of CAT were present within 2 h of dosing (21.3 +/- 7.2 pg, n >/= 8, mean +/- SD). The results confirm that DNA-DOTIM:cholesterol complexes are initially deposited in the lungs after iv administration.     

Analysis of T-DNA-mediated translational beta-glucuronidase gene fusions

Using polymerase chain reaction (PCR) with back-to-back primers, 85 different mitochondrial DNA (mtDNA) rearrangements, consisting of partial duplications or mini-circles, were detected in brain, liver, and heart tissue from Fischer 344 rats. The regions around the mitochondrial tRNALeu(UUR) gene, the cluster of three tRNA genes [His, Ser(AGY), Leu(UUC)], as well as the region of the displacement loop were analyzed separately with different primer sets. Rearrangements were detected in all regions analyzed in samples taken throughout the animal life span, ranging from 1 day old to 33 months of age (senescent). Two-thirds of the rearrangements terminated at short (3-9-bp) direct repeats. Three of the different rearrangements were detected in more than one animal; the most common rearrangement was found in nine different template preparations. Two loci (hot spots) were found to be particularly susceptible to rearrangement, and both were located at sequences that exhibited highly conserved potential for secondary structure formation. The displacement loop region of 10 samples exhibited the presence of multiple tandem duplications ranging between 324 and 449 bp in length. One of these consisted of heterologous, but overlapping, repeating units. Identical PCR protocols were carried out in control experiments using a cloned fragment of mtDNA that encompassed the most common hot spot sequence. The results showed that this fragment did not artifactually generate a rearrangement junction under our PCR conditions and suggested that this sequence does not promote rearrangement mutations in bacteria during the cloning process.     

Behavioral markers and recognizability of the smile of enjoyment

Several age-dependent modifications of inner mitochondrial membrane and synaptosomal plasma membrane proteins from different brain regions of 4-, 12-, 18- and 24-month-old male Wistar rats, were observed. Some proteins, identified by immunoblotting assay as various subunits of mitochondrial respiratory chain complexes and calmodulin, were particularly impaired. Chronic treatment with CDP-choline at a dose of 20 mg/kg body weight per day for 28 days caused significant changes in the amounts of several of the above mentioned proteins. Most of the proteins, which decreased during aging, showed a significant increase after CDP-choline treatment compared with the corresponding control values at the same age. The effect of CDP-choline might be due to: the increased availability of cytidylic nucleotides, which in the brain are present in limited amounts compared to the other nucleotides; the increased content of total adenine nucleotides; the improvement of brain energy metabolism.     

Global cerebral ischemia and reperfusion alters NMDA receptor binding in canine brain

We employed a canine model to test whether binding to the N-methyl-D-aspartate (NMDA) class of glutamate receptor channels is altered by global cerebral ischemia and/or reperfusion. Ischemia was induced by 10-min cardiac arrest, followed by restoration of spontaneous circulation for periods of 0, 0.5, 2, 4, and 24 h. In vitro autoradiography was performed on frozen brain sections with three radioligands: [3H]glutamate (under conditions to label the NMDA site), [3H]glycine, and [3H]MK-801. Modest decreases in [3H]glutamate and [3H]MK-801 binding were seen in several regions of hippocampus, and parietal and temporal cortex at early times after reperfusion, with values returning toward control by 24 h. In the striatum, a different pattern was seen: [3H]glutamate and [3H]MK-801 binding increased 50-200% at 0.5-4 h after the start of reperfusion, returning toward control levels by 24 h. These increases correlate with findings of increased sensitivity to NMDA-stimulated release of dopamine from striatal tissue in the same model (Werling et al., 1993), and suggest that changes in tissue receptors may contribute to the selective vulnerability to ischemic damage during the first hours following reperfusion.     

Content of mutant mitochondrial DNA and organ dysfunction in a patient with a MELAS subgroup of mitochondrial encephalomyopathies

A point mutation of mitochondrial tRNALeu(UUR) gene is responsible for a MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) subgroup of mitochondrial encephalomyopathies. In most cases, the mutant mitochondrial DNA (mtDNA) coexists with normal mtDNA in a heteroplasmic manner. In order to quantify the content of mutant mtDNA, we developed a quantitative method of PCR. Using this method, the distribution of the mutant mtDNA was examined in 32 different tissues among 18 autopsied organs from a patient with MELAS, who had shown hypophyseal dysfunction. The percentage of the mutant mtDNA at nucleotide number 3243 in each tissue was ranged between 22% and 95%. The content of the mutant mtDNA was at the highest (95%) in the hypophysis and higher in the cerebral cortex than in the white matter. This study shows a possible correlation of tissue dysfunction with accumulation of the mutant mtDNA within the brain.     

A clinico-neuropathological study on brain death

A clinico-neuropathological study was conducted on 60 cases of brain death, 36 males and 24 females, ranging in age from 11 to 81 years, the average being 49.4 years. Of these, 29 patients died of cerebrovascular disease. The average duration of brain death was 99 hours. The mean weight of the brain was 1466 g. Neuropathological findings were brain edema, congestion, herniation and various subarachnoid hemorrhages. Histologically, the cytoplasm of neurons was pale and ghost-like. In the white matter, myelin staining was pale, and nuclei of the glial cells were shrunken and piknotic. Autolysis of the cerebellar granular layer and the pituitary gland was evident in all cases. No reactive astrocytosis or infiltration of the cells in or around necrotic tissue could be seen. In eight cases, there was laminar infiltration of neutrophils in the superficial area of the cerebrum and brain stem, possibly due to temporary or partial recirculation. Correlation between the degree of autolysis and duration of brain death was observed, but no relationship between the degree of autolysis and the difference of underlying disease could be found. Autolysis in the cerebral cortex, thalamus, tegmentum of the brain stem, cerebellar granular layer and pituitary gland was most prominent. However, neuropathological diagnosis of underlying diseases could be made even in brain death. Histologically, the cases of brain death differed from those of cardiac arrest-induced encephalopathy and from those of long postmortem autopsy.     

A powerful nonviral vector for in vivo gene transfer into the adult mammalian brain: polyethylenimine

Nonviral gene transfer into the central nervous system (CNS) offers the prospect of providing safe therapies for neurological disorders and manipulating gene expression for studying neuronal function. However, results reported so far have been disappointing. We show that the cationic polymer polyethylenimine (PEI) provides unprecedentedly high levels of transgene expression in the mature mouse brain. Three different preparations of PEI (25-, 50-, and 800-kD) were compared for their transfection efficiencies in the brains of adult mice. The highest levels of transfection were obtained with the 25-kD polymer. With this preparation, DNA/PEI complexes bearing mean ionic charge ratios closest to neutrality gave the best results. Under such conditions, and using a cytomegalovirus (CMV)-luciferase construction, we obtained up to 0.4 10(6) RLU/microgram DNA (equivalent to 0.4 ng of luciferase), which is close to the values obtained using PEI to transfect neuronal cultures and the more easily transfected newborn mouse brain (10(6) RLU/microgram DNA). Widespread expression (over 6 mm3) of marker (luciferase) or functional genes (bcl2) was obtained in neurons and glia after injection into the cerebral cortex, hippocampus, and hypothalamus. Transgene expression was found more than 3 months post-injection in cortical neurons. No morbidity was observed with any of the preparations used. Thus, PEI, a low-toxicity vector, appears to have potential for fundamental research and genetic therapy of the brain.     

Whole-body kinetics and dosimetry of L-3--123I-iodo-alpha-methyltyrosine

BACKGROUND: Desflurane anesthesia can produce cerebral metabolic depression and increase cerebral blood flow. We evaluated the effect of desflurane on brain tissue oxygen pressure (PO2), carbon dioxide pressure (PCO2) and pH during neurosurgery. METHODS: Following a craniotomy, the dura was opened and a Paratrend 7 sensor, which measures PO2, PCO2, pH and temperature, was inserted into brain tissue. In 6 control patients in group 1, anesthesia was maintained constant with 3% end-tidal desflurane over 60 min, including a 30-min stabilization period. In group 2, 9 patients were ventilated with 3% desflurane under baseline conditions. After a 30-min stabilization period, baseline tissue gases and pH were measured and end-tidal desflurane was increased to 6% and then 9% for 15-min intervals. Mean arterial pressure (MAP) was maintained with intravenous phenylephrine. RESULTS: Under baseline conditions, cardiovascular and brain tissue measures were similar between the 2 groups. Increasing end-tidal desflurane from 3% to 9% produced burst-suppression EEG in all patients and significantly increased tissue PO2 and pH and decreased PCO2. No parameters changed significantly in the control group during steady-state anesthesia. CONCLUSION: These results show that 9% desflurane can improve brain tissue metabolic status before temporary brain artery occlusion if cerebral perfusion pressure is maintained. This may be particularly important in patients with symptoms of ischemia before surgery.     

Cytosolic redistribution of cytochrome c after transient focal cerebral ischemia in rats

Recent in vitro cell-free studies have shown that cytochrome c release from mitochondria is a critical step in the apoptotic process. The present study examined the expression of cytochrome c protein after transient focal cerebral ischemia in rats, in which apoptosis was assumed to contribute to the expansion of the ischemic lesion. In situ labeling of DNA breaks in frozen sections after 90 minutes of middle cerebral artery (MCA) occlusion showed a significant number of striatal and cortical neurons, which were maximized at 24 hours after ischemia, exhibiting chromatin condensation, nuclear segmentation, and apoptotic bodies. Cytosolic localization of cytochrome c was detected immunohistochemically in the ischemic area as early as 4 hours after 90 minutes of MCA occlusion. Western blot analysis of the cytosolic fraction revealed a strong single 15-kDa band, characteristic of cytochrome c, only in the samples from the ischemic hemisphere. Western blot analysis of the mitochondrial fraction showed a significant amount of mitochondrial cytochrome c in nonischemic brain, which was decreased in ischemic brain 24 hours after ischemia. These results provide the first evidence that cytochrome c is being released from mitochondria to the cytosol after transient focal ischemia. Although further evaluation is necessary to elucidate its correlation with DNA fragmentation, our results suggest the possibility that cytochrome c release may play a role in DNA-damaged neuronal cell death after transient focal cerebral ischemia in rats.     

Insulin receptors are widely distributed in human brain and bind human and porcine insulin with equal affinity

Insulin receptors differing structurally from those in other tissues have been demonstrated in brain from many species. Subtle differences in binding properties have been reported between insulin receptors in brain and other tissues, including differences in affinity of pig brain receptors for human and porcine insulin. Insulin binding has been demonstrated in human cerebral cortex, but insulin binding has not been characterized in other areas of human brain. We have studied the binding of 125I labelled human insulin, and its displacement by unlabelled human and porcine insulin, in homogenates prepared from human hypothalamus, cerebral cortex and cerebellum obtained post-mortem from eight non-diabetic subjects. Specific binding was demonstrated in all brain regions studied, and displacement curves obtained with unlabelled human and porcine insulin were identical. By contrast, unlabelled insulin-like growth factor-1 did not significantly displace 125I labelled human insulin over the same concentration range. We therefore conclude that insulin receptors are widely distributed in human brain and do not differ in their affinity for human and porcine insulin.     

Fluorometric assay of nitrite and nitrate in brain tissue after traumatic brain injury and cerebral ischemia

Nitric oxide synthase (NOS) is distributed within the brain, and nitric oxide (NO) is felt to be involved in the pathophysiology of deterioration after head injury and cerebral ischemia. This study determined the levels of the stable end products of NOS (NOx=nitrite+nitrate) after traumatic brain injury (TBI) and transient cerebral ischemia. A fluorometric assay using nitrate reductase and the NADPH regenerating system was used to quantitate NOx in ultrafiltered (10-kDa cutoff) cortical and hippocampal extracts after reduction of nitrate. In TBI rats, both the plasma and tissue showed a sharp increase in NOx levels 5 min after injury. Plasma NOx returned to control levels by 2 h after injury. Ipsilateral-cortex NOx levels returned to control levels approximately 6 h after injury and remained constant from 6-24 h. Contralateral-cortex returned near to control levels after 1 h. Hippocampus also followed a similar trend. In gerbils, there was a significant elevation in tissue NOx levels immediately after 10 min transient cerebral ischemia, which gradually returned to control levels over 24 h reperfusion. This striking burst of NO synthesis immediately after injury is clearly evident whether the injury is head trauma or ischemia, or whether the measurements were performed on tissue or plasma. It is unknown whether endothelial NOS, neuronal NOS, or both caused the elevation of the NO end products seen after the CNS insults.     

C-Fos, Jun D and HSP72 immunoreactivity, and neuronal injury following lithium-pilocarpine induced status epilepticus in immature and adult rats

In order to follow the maturation-related evolution of neuronal damage, cellular activation and stress response subsequent to Li-Pilo seizures in the 10- (P10), 21-day-old (P21) and adult rat, we analyzed the expression of the c-Fos protein as a marker of cellular activation, HSP72 immunoreactivity as the stress response and silver staining for the assessment of neuronal damage in 20 selected brain regions. The early wave of c-Fos measured at 2 h after the onset of seizures was present in most structures of the animals at the three ages studied and particularly strong in the cerebral cortex, hippocampus and amygdala. The late wave of c-Fos measured at 24 h after the onset of seizures and that was shown to correlate to neuronal damage was absent from the P10 rat brain, and present mainly in the cerebral cortex and hippocampus of P21 and adult rats. The expression of the stress response, assessed by the immunoreactivity of HSP72 at 24 h after the seizures was absent from the P10 rat brain and present in the entorhinal cortex, amygdala, hippocampus and thalamus of P21 and adult rats. The expression of Jun D at 24 h after the seizures was discrete and present in most brain regions at all ages. Neuronal injury assessed by silver staining at 6 h after the onset of seizures was very discrete in the brain of the P10 rat and limited to a few neurons in the piriform and entorhinal cortices. In older animals, marked neuronal degeneration occurred in the cerebral cortex, amygdala, hippocampus, lateral septum and thalamus. Thus the immediate cell activation induced by lithium-pilocarpine seizures which is present at all ages translates only into a late wave of c-Fos and the expression of HSP72 in P21 and adult animals in which there will be extensive cell damage.     

Consequences of gamma-irradiation on inflammatory cytokine regulation in human monocytes/macrophages

We have investigated mitochondrial DNA (mtDNA) mutagenesis in the laboratory mouse. Using a nested PCR method for quantification, the absolute frequency, tissue distribution and rate of increase of mitochondrial deletion mutations was determined. Multiple deletions arise in brain, cardiac muscle and kidney tissues: deletions occur most frequently at regions of directly repeated mtDNA homology. Deletion frequencies rose by 2.5 x 10(5), 6300- and 4000-fold in heart, brain and kidney, respectively, between young and old mice. The rates of mtDNA mutation accumulation in mouse and human hearts are modeled well by exponential equations, with r-values of 0.96 and 0.97, and mutations rose much faster in mouse than human mtDNA per unit time. Thus, maintenance of the human mitochondrial genome is much better than that of mice, consistent with the higher rate and final extent of total DNA repair in humans than mice, that has been observed by others and consistent with the predictions of the disposable soma model of aging. A comparison of mtDNA mutagenesis from cardiocytes vs. whole heart tissue was undertaken. Deletion mutations were observed to be 100-fold lower in DNA prepared from isolated cardiocytes than from whole heart homogenates, consistent with a model of uneven mtDNA mutation accumulation.     

Hypoxic preconditioning and hypoxic-ischemic brain damage in the immature rat: pathologic and metabolic correlates

It has been reported that immature rats subjected to cerebral hypoxia-ischemia sustain less brain damage if they are previously exposed to systemic hypoxia compared with animals not exposed to prior hypoxia. Accordingly, neuropathologic and metabolic experiments were conducted to confirm and extend the observation that hypoxic preconditioning protects the perinatal brain from subsequent hypoxic-ischemic brain damage. Six-day postnatal rats were subjected to systemic hypoxia with 8% oxygen at 37 degrees C for 2.5 h. Twenty-four hours later, they were exposed to unilateral cerebral hypoxia-ischemia for 2.5 h, produced by unilateral common carotid artery ligation and systemic hypoxia with 8% oxygen. Neuropathologic analysis, conducted at 30 days of postnatal age, indicated a substantial reduction in the severity of brain damage in the preconditioned rats, such that only 6 of 14 such animals exhibited cystic infarction, but all 13 animals without prior preconditioning exhibited infarction (p < 0.001). Measurement of cerebral glycolytic and tricarboxylic acid intermediates and high-energy phosphate reserves at the terminus of and at 4 and 24 h following hypoxia-ischemia showed no differences in the extent of alterations in the preconditioned and nonpreconditioned immature rats. A difference was seen in the restitution of high-energy stores during the first 24 h of recovery from hypoxia-ischemia, with a more optimal preservation of these metabolites in the preconditioned animals, reflecting the less severe ultimate brain damage. Accordingly, the neuroprotection afforded to the preconditioned animals was not the result of any differences in the extent of anaerobic glycolysis, tissue acidosis, or depletion in high-energy reserves during hypoxia-ischemia but rather the result of other mechanisms that improved the metabolic status of the immature brain during the early hours of reperfusion following hypoxia-ischemia.